Recently I bought a new monitor and I connect it to my laptop through HDMI. When I use laptop monitor everything was fine. But the external one is really glitchy like in this video
https://drive.google.com/file/d/1NrmDIzBfQ4a1sPGeaZ7_dpiJtO3Jkmdq/view?usp=drivesdk
Even when shutdown it's still glitch.
The splash screen glitch is similar to my experiment when combine lightdm with plasma (I'm switch back to sddm and everything work fine, but I still don't know why It's have the glitch but maybe it's for another topic).
I use intel-nvidia-prime-450.66 install by mhwd, my nvidia card is Geforce 940MX.
Plasma version: 5.19.5
KDE frameworks: 5.73.0
Qt: 5.15.0
Kernel: 5.8.6-1-Manjaro
Somebody please help me with this :frowning:
Sorry for my English, it's not my nature language.

I assume you ruled out a problem with the HDMI cable (these can be tricky beast, often just turning it around can solve issues).

Did you try a different NVIDIA driver? The proprietary drivers are notoriously bad with Linux, you usually get better results with the nouveau driver.